The clinical finding of bilateral symmetrical shallow corneal ulcers in a child with tyrosinemia led to this study. A number of such cases have been described in the literature as "Richner-Hanhart Syndrome" because of hyperkeratosis of the palms and soles associated with corneal ulcers. The rat fed an excess of dietary tyrosine develops both these anomalies. This investigation has characterized by light and electron microscopy the histopathology of the cornea in this syndrome and is beginning to investigate by electron microscopy the ultrastructure of the cornea to determine which anatomic components of the corneal epithelium and stroma are involved. Levels of serum tyrosine are being monitored in order to determine the direct relationship between serum tyrosine and corneal disease. It has been found that the corneal pathologic changes induced by high tyrosine diet can be blocked by high doses of adrenal cortico- steroids. Further investigation of the influence of the adrenal glands upon this phenomenon are under way. Additionally, blocking the C3 component of complement with cobra venom factor is being done to elucidate the role of this factor of complement in the inflammatory and degenerative processes of the cornea that are involved.